[HIV incidence in a cohort of homosexual men and a cohort of injecting drug users in Amsterdam, 1985-1995].

Since 1984/1985 a cohort of homosexual men (HM; n = 770 initially HIV-seronegative) and one of injecting drug abusers (IDU; n = 675 initially seronegative) are being followed in Amsterdam, in order to assess the HIV epidemic in these high-risk groups. The HIV incidence in HM fell from 7.2/100 person years in 1985 to 1.0 in 1989, due to safer sexual behaviour. In 1990 there was a temporary rise in HIV incidence coinciding with an increase in gonorrhoea and syphilis in homosexual/bisexual men (not in the cohorts) attending a sexually transmitted diseases outpatient clinic. The rise was due to a relapse in unsafe sexual behaviour. After 1990 the HIV incidence dropped again and it remained at 1/100 person years in 1995. In IDU, in whom a reduction was found in both injecting and sexual risk behaviour, the incidence fell from 8.9 in 1986 to 2.0-3.6/100 person years in 1991-1995. In order to follow the future course of the HIV epidemic, it is argued to open the cohorts particularly for young HM and IDU.